Wednesday, December 9, 2009

Living the Radiant Life

Living in a straw bale house, we get a lot of questions. These range from the comical "Three Pigs" type allusions, to the more serious, "Isn't it a fire hazard to have straw in your walls?" Once people realize that the straw serves as insulation, they want to know how warm the house is. As in all the homes we've lived we keep the temperature around 68 degrees Fahrenheit. We could certainly keep it warmer, but we try to treat heat as the valuable resource it is. Hence my ever-growing collection of wool cardigans.

When people ask how warm our house is, I think what they really want to know is how much energy we are saving. Until we've lived here a year we won't have a definitive answer to that. According to Chris Magwood in his book Straw Bale Building, "Insulation values (commonly referred to as R-values) for conventional residential wall systems typically range between R-12 and R-20, depending on climactic conditions. Straw bale walls have R-values between R-35-R-50, depending on their width." In that way, using straw bales for insulation has allowed us to significantly reduce the amount of energy required to heat and cool a house this size.

Haven Homestead is designed to operate on two heating sources. The first is a radiant floor system, fueled by propane. The second is a woodburning Finnish masonry heater. These two heat sources will work together in the future; the masonry heater is not yet online. We look forward to firing it up next winter, fueling it with wood split from our homestead. This will allow us to dramatically reduce our reliance on propane.

There are many positive aspects of living with a radiant floor. Extremely quiet systems, we don't hear the rush of the furnace turning on, the drone of air whooshing through a register. Gone are the days of itchy skin and nosebleeds from air that is overdried from a forced air system. Radiant systems are also hidden from sight in the subfloor; not only visually pleasing, this also makes them extremely childproof. They aren't prone to large fluctuations in temperature and distribute heat evenly.

For those of you who may have never experienced a radiant floor, ours is an open direct system designed with components from the Radiantec company based in Vermont. "The system uses one very efficient water heater to make domestic hot water for the home and warm water for radiant heating. Radiant heating systems warm the building by locating heating tubes within a large surface area of the building and then circulating warm water through the tubes." (Radiantec Open Direct System Installation, pg. 1) When the construction of the masonry heater is complete the two systems will work in concert, with heating coils for the floor running through the fireplace. This will preheat the water before it arrives at the hot water tank, reducing the amount of heat needed (and the amount of propane used) to bring the water in the hot water tank up to the desired temperature.

Two of the largest advantages for us in choosing a radiant floor heating system were ease of installation and system cost. According to the brochure we obtained from Radiantec, "Installation of radiant heat does not have to be hard, and it does not have to be expensive." They go on to say, "Radiantec Company thinks that the task of installing underfloor radiant heat is the task of a reasonably competent handyman...and that the work can be done with common, readily available tools." I would consider their opinion correct on both counts. Though we did have a licensed plumber help install the hot water manifold, Todd and my father were able to complete the actual installation of the floor elements. Radiantec designed the layout; we placed strapping across the entire subfloor and laid the Pex tubing between the strapping members. We filled the cavities next to the Pex tubing with sand. (Sand was chosen for its excellent heat retention and relatively low cost, as well as the fact that it requires no additional manufacturing, as is the case with cement.) We covered the entire first floor with cement backer board and laid ceramic tile wall-to-wall.

Regarding system cost, our expense for purchasing the components of the system (Pex tubing, manifold, reflective barrier, couplings, pump, all valves, digital temperature display, pressure gauges, etc.) ran around $2,400. An additional $1,696 was needed to purchase the hot water tank, bringing the total component cost to $4,096. (Note, in an effort to save in construction costs, we opted for a less expensive water heater than the extremely efficient Polaris recommended by Radiantec, with the intent to replace it with a Polaris in the future.) At the time we purchased the materials for our system a comparable conventional baseboard hot water system would have cost us approximately $6,500 (Radiantec Heating Systems, pg. 3).

Although it was not my intent to turn this post into an advertisement for Radiantec, we've been very pleased with our team effort to design and install Haven's radiant floor. Radiantec is a member of the International Code Council. They offer assistance designing systems, help with materials specification, and provide detailed installation manuals. They also provide unlimited toll-free technical support for as long as you own your system. Our house is warm and draft-free. As our son is often wont to do, you can walk across the ceramic tile in your bare feet in winter with a level of comfort.

Taken just this morning, featuring Batman pajamas and bare feet.


Magwood, Chris and Peter Mack. Straw Bale Building: How to Plan, Design and Build With Straw. Gabriola Island: New Society Publishers, 2002.

Radiantec Incorporated
Box 1111, Lyndonville, Vt 05851
(800) 451-7593
FAX (802) 626-8045

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